Yes, one can control what level the IMGR009 message is through an option in the ENCOPTBL table located in the Endevor CSIQSRC library.
In the ENCOPTBL source is the following line:
* ENHOPT MSGSEVERITY_IMGR009=E W/E O000503
One just needs to uncomment the line, change it to =W, and reassemble the table.
The default for the message is an E-level.